RPM/Prop Problem

Alyssa Jean · Posted: Sun Dec 19, 2004 4:26 pm Post subject: RPM/Prop Problem

Need some advice.

While cruising yesterday on the Lake Wash outing at about 5 MPH I got both props tangled tightly with a large piece of plastic sheeting that was floating just under the surface. It immediately killed both engines. Didn't break any blades. (Honda 40s with ProPulse Props. I was able to cut the plastic loose and engines started and ran fine for the next hour at 7 MPH ( Came through the Ballard Locks and into Lake Wa. in 7 MPH No Wake Zone for two miles)
Upon entering the lake I moved the throttles forward to get up to about 22 MPH cruise speed. The port engine raced to 6000 RPM and the starboard stopped at about 5000 . I backed off quickly and advanced slowly to get up to speed. Could only get about 17 MPH at 5000. The throttles had to be in different positions to get 5000 on each. Had to back off the port side or it would go to 6K again. Pulled the props
this morning and can see nothing obviously wrong. Any idea what I did. Is there a slip linkage in the drive shaft that I may have torn up?

Captains Cat · Posted: Sun Dec 19, 2004 6:02 pm Post subject:

David, hard to diagnose from the Right Coast. Not being familar with the adjustment of pitch on your wheels, could the plastic encounter have changed the pitch on one or more blades? If there's no apparent damage, that's all I can think of.

Good luck, I've got twins, let us know what you find.

Charlie
K4KBA

TyBoo · Posted: Sun Dec 19, 2004 6:05 pm Post subject:

Probably so obvious that you have already checked/verified, but it sounds to me like the props have different pitches. Quite possible with those adjustable ProPulse jobs. I suppose there could be a problem in the hub of one prop, but I don't know how they are constructed. A quick check would be to put your original aluminum props back on for your next outing.

I don't think it is anything inside the gear case. I do believe they will either work or not work.

Larry H · Posted: Sun Dec 19, 2004 6:05 pm Post subject:

Aluminium and stainless props are build with a rubber sleeve between the hub and the prop. This sleeve slips if the prop hits something, in order to save the gears and shafts.

I don't know if the Propluse prop has such a sleeve or if they depend on the blades breaking off to save the gears and shafts.

I would inspect the splined area of the prop hub carefully and also check the pitch setting on the blades.

If this doesn't show anything, switch the props port to starboard and see if the problem follows the prop or not.

Hope this helps.

Alyssa Jean · Posted: Sun Dec 19, 2004 6:37 pm Post subject:

All good thoughts. The ProPulse does not have a hub that can spin. It is a solid molded hub. I have checked the settings and they are set the same as before with no shift or change. The splines appear to be all intact with no change there.
I do have one other, and soon two, ProPulse hubs because Pat on Daydream changed back to aluminum. So the best thing so far is to swap the existing props and see if the problem moves from port to starboard.

Will keep you tuned in.

Alyssa Jean · Posted: Mon Dec 27, 2004 9:38 am Post subject:

Here is the follow-up on the prop problem.

The ProPulse prop is a composite prop with several moving and adjustable parts enabling the owner to adjust the pitch of the prop to the needs of the boat. The prop is made up of several parts. Closest to the engine is splined hub into which the four blades fit. After the blades are in place another piece fits over the blades and up tight to the inner hub, holding the blades into position . There are markings under each blade on the outside so you know where the adjustment is in relation to each other, althought they all move in or out together. Then there is a tail piece with a slightly flared end which looks like the end of an exhaust pipe. There are four allen head long screws which hold it all together. The heads of the screws also hold on the tail piece . Normally you back off the screws about 4 turns and re-adjust the pitch.

When I got tanbled up very tightly in the plastic sheeting the engines stalled immediately. The tail piece on the port engine was forced off and was lost. The tail piece is only held on by the four screw heads over lapping the inside edge of the tail piece. This I think allowed the heads of the screws to be loose on the prop hub and allowed the pitch to change to a lesser degree. So when I went to full RPM the port engine just "took off".

I disassmbled the prop and found nothing cracked, tweaked or unusual, and put it back together with a new tail piece and all is well. I think actually I could have got back to the correct pitch by re-adjusting the prop blades and re-tightening the screws and replaced the tail piece later.

Chuck S · Posted: Mon Dec 27, 2004 11:23 am Post subject:

Should there be washers under the Allen screws to help secure this all to the shaft?

-- Chuck

Alyssa Jean · Posted: Mon Dec 27, 2004 7:31 pm Post subject:

Yes there should be, and they are there.

Anita Marie · Posted: Mon Dec 27, 2004 8:03 pm Post subject:

David, glad you were able to ID the problem. I have checked mine and tightened them up.